William Gilbert was born in Colchester, Essex, England, on May 24, 1544. Although he was trained as a doctor and appointed court physician for a short time to both Queen Elizabeth I and King James I, Gilbert made his mark in the study of magnetism. His book De Magnete ("Concerning Magnetism"), established him as a physicist.

Petrus Peregrinus laid the groundwork of the understanding of magnetism some 250 years earlier. Gilbert built upon that framework. Like Peregrinus, Gilbert believed in experimentation to prove or disprove theory. Galileo credited Gilbert with being the founder of the experimental method, although history credits Galileo.

Gilbert discovered that a magnetic compass needle not only pointed north and south, it also "dipped" downward when influenced by a spherical magnet. He went on to discover that if the needle was freely suspended it "dipped," pointing toward the Earth. This "magnetic dip" led Gilbert to conclude that the...